Cool, a dimmer will work for now. Just make sure that you check the temperature where the UTH is without the substrate to make sure it's 90F or lower. I also recommend getting a digital thermometer/hygrometer so you can monitor ambient temps and humidity. This is the one I use which is pretty accurate. You can probably find it at Walmart or a home improvement store a little cheaper.
http://www.acurite.com/digital-humid...tor-00309.html